Page 1of 4 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Response: Rocky Flats Plant Health 

Surveillance Document Review 

White Paper 

Rev. 1 

National Institute for Occupational 

Safety and Health 

May 30, 2014 

J. S. Bogard, E. M. Brackett, Mutty Sharfi, and Dan Stempfley 

Oak Ridge Associated Universities Team 

- 

Reviewed by Dr. James W. Neton and LaVon B. Rutherford, CHP 

Division of Compensation Analysis and Support 
White Paper Response: Rocky Flats Health Surveillance Document Review June 3, 2014

Page 2 of 4

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

PURPOSE AND BACKGROUND

This is an assessment and response to petitioner allegations that Rocky Flats Plant (RFP) 

dosimetry records cannot be relied upon for dose reconstruction. The petitioner refers to a 2006 

Oak Ridge Institute for Science and Education (ORISE) document, Health Surveillance of Rocky 

Flats Radiation Workers, and notes that the document Summary indicates that approximately 

10% of these former workers were found to have received internal exposures higher than 

reported in Health Physics records (Site Research Database (SRDB) 126999, pdf p. 5). The 

Division of Compensation Analysis and Support (DCAS) directed the Oak Ridge Associated 

Universities Team (ORAUT) to review this surveillance document and provide a response

concerning this issue.

ORAUT identified a 2004 document, Final Report – Former Radiation Worker Surveillance at 

Rocky Flats, that expands on the allegation currently under review. This document states:

The physical review of health physics files from 1952 through 1976, in conjunction with the 

file reviewers’ a priori knowledge of plant operations, led to the discovery that the health 

physics files did not always reflect an individual’s complete exposure status...

...Approximately ten percent of the 1,164 participants for whom a dose assessment was 

performed were determined to have some unrecorded internal dose, and approximately five 

percent of the participants had a significant unrecorded dose. A significant dose, for the 

purpose of this report, was a dose value of 20 rem or more. One percent of the participants 

had an unrecorded internal dose that exceeded 100 rem. The most noteworthy case was a 

mid-level manager in a major plutonium processing building in the 1950’s, whose TEDE of 

over 500 rem places him seventh on high-to-low TEDE list for participants. The records in 

his Rocky Flats health physics file and in his medical file are mute regarding the plutonium 

contamination incident he described in his interview. (SRDB 121677, pdf pp. 24-25)

The issue of dose refinement as a result of worker recall programs is discussed in SEC-00030, 

Rocky Flats Plant Evaluation Report, Section 7.5.1.6, Worker Recall Monitoring Program,

which specifically mentions the Former Radiation Worker Medical Surveillance Program at 

Rocky Flats. The discussion states:

Bioassay results from recall programs can help refine estimates of dose from internallydeposited radioactive materials. However, the ability of NIOSH to perform dose 

reconstructions is not predicated on the continuance of such programs. When these data are 

available, NIOSH will consider them in dose reconstructions, but monitoring and other data 

collected from the period during which the worker was employed, together with NIOSH’s 

procedures for the assignment of unmonitored doses, are sufficient to conduct dose 

reconstruction. (SEC-00030, RFP ER, Rev. 0 Final, 04-07-06, pdf p. 71)
White Paper Response: Rocky Flats Health Surveillance Document Review June 3, 2014

Page 3 of 4

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

OBSERVATIONS

For radiological dose reconstructions performed under the Energy Employees Occupational 

Illness Compensation Program Act (EEOICPA) program, internal dose is calculated based on an 

individual’s bioassay results (for the most part, using different models based on all 

available/related information, as compared to what would have been used/available at the time 

by the site); the site’s dose of record is not used.

Two points need to be made about differences in calculated dose using different methods at 

different historical times under different programs:

1. The apparent difference in dose from the early years (i.e., dose assessed by the site) 

compared to later years (i.e., dose assessed in follow-up efforts described in the ORISE 

Health Surveillance and RFP Worker Surveillance documents) primarily results from the 

historical difference in Minimum Detectable Activity (MDA) for bioassay samples; 

more-recent samples have lower MDAs due to the increased precision of modern equipment. 

Lower MDAs result in better accountability of internal exposure and better quantification of 

intake activities compared to early site assessments. Whereas the site’s early-years 

monitoring efforts with higher detection limits might result in “<MDA” recorded values and 

no dose assignment, later-year assessments performed with more-sensitive instruments might

result in the assignment of doses. More specifically, the ORISE Health Surveillance report is 

taking original site-calculated doses and comparing them to recalculated external and internal 

dose based on new bioassay data from the medical monitoring program as well as data from 

the Neutron Dose Reconstruction Project (NDRP). The report finding that the internal 

exposures are higher than reported in the HP record reflects the lesser sensitivity of the 

historical detection limits. When workers were re-sampled during the medical monitoring 

program, the sensitivity of the more-recent bioassay was much better. Therefore, it is not 

surprising that intakes that were not detected by the site during the time of intake were 

detected with more contemporary analysis methods decades later, thus resulting in 

assignment of more doses or higher doses. 

2. There are two additional differences between doses assigned by either the historical site 

program or the follow-up ORISE Health Surveillance program as compared to EEOICPA 

dose reconstructions. First, the EEOICPA program assigns missed dose, which accounts for 

any limitations in analytical measurements by calculating the maximum dose that could have 

gone undetected. Second, the EEOICPA program can assign dose based on EEOICPAdeveloped co-worker studies, which can be used to account for unmonitored dose by 

assessing and assigning a calculated dose based on co-located personnel data. Therefore, the 

EEOICPA dose reconstructions result in two additional dose assignments that are not 

covered by either of the aforementioned assessments.
White Paper Response: Rocky Flats Health Surveillance Document Review June 3, 2014

Page 4 of 4

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

CONCLUSION

The potential undetected intakes at RFP discussed in the ORISE Health Surveillance Report 

result from the use of more-sensitive instruments in later years. The surveillance report does not 

indicate that the RFP internal monitoring program was inaccurate and thus the information not 

usable. The EEOICPA dose reconstruction processes assess reliable and usable data to account 

for all potential exposures and determine bounding intakes – including unmonitored exposures -

through the use of missed-dose and possibly co-worker dose assignments, which are not 

considered in the historical or follow-up dose assessments. Therefore, the conclusion is that all 

potential dose is accounted for, and the findings of the Health Surveillance Report do not impact 

the ability to reconstruct dose with sufficient accuracy under the NIOSH EEOICPA radiological 

dose reconstruction program.